The present invention concerns intermediate compounds useful in the preparation of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (CMHEIDA), also referred to as carboxymethoxyhydroxyethylimino diacetic acid.
Chelants or chelating agents are compounds which form coordinate-covalent bonds with a metal ion to form chelates. Chelates are coordination compounds in which a central metal atom is bonded to two or more other atoms in at least one other molecule or ion, called a ligand, such that at least one heterocyclic ring is formed with the metal atom as part of each ring.
Chelating agents for metal ions, such as calcium, magnesium, iron, and magnesium, are required for a wide range of technical fields. Examples of fields of application and end-uses of chelants are detergents, in electroplating, in water treatment, photography, textile industry, paper industry and also various uses in pharmaceuticals, cosmetics, foodstuffs and plant nutrition. Some of these activities may result in the chelating agents entering the environment. For example, agricultural uses or use in detergents may result in measurable quantities of the chelants in water.
As chelants many enter the environment from various uses, it is desirable to have chelants that would readily degrade after use. It would be particularly advantageous to have a chelant which is biodegradable, that is, susceptible to degradation by microbes which are generally naturally present in environments into which the chelants may be introduced.
Iminodiacetic acid derivatives are known to possess metal sequestering properties. U.S. Pat. No. 5,051,212 discloses that iminodiacetic acid derivatives, when combined with organic solvents, provide very good results in terms of soil removal from hard surfaces. The use of iminodiacetic acid derivatives in aqueous compositions for cleaning hard surfaces is reported in PCT Application No. WO 94/12606. The iminodiacetic acid derivatives in WO 94/12606 are also reported to have good biodegradable characteristics.
The present invention concerns compounds represented by the formula 
wherein R and R1 independently represent H, xe2x80x94CH2CN or xe2x80x94CH2CO2X, with the proviso that R and R1 can not be both H or xe2x80x94CH2CO2X; and X represents hydrogen, an alkali metal or alkaline earth metal.
In another aspect, the present invention concerns a process for the preparation of N-[2-(carboxymethoxy)ethyl]aminoacetonitrile (III) which process comprises alkylating 3-morpholinone with formaldehyde and hydrogen cyanide or glycolonitrile under alkaline conditions.
Still in another aspect, the present invention concerns a process for the preparation of N-[2-(carboxymethoxy)ethyl]glycine (V) which process comprises hydrolyzing an aqueous solution of a compound of the formula: 
wherein X is hydrogen or an alkali or alkaline-earth metal with an acid or base.
Still in another aspect, the present invention concerns a process for the preparation of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (Formula IX) which process comprises hydrolyzing an aqueous solution of a compound of the formula: 
wherein X is hydrogen or an alkali or alkaline-earth metal with an acid or base.
In another aspect, the present invention concerns a process for the preparation of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX) which process comprises reacting (2-aminoethoxy)acetic acid with glycolonitrile or hydrogen cyanide and formaldehyde under alkaline conditions.
Still in another aspect, the present invention concerns a process for the preparation of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX) which process comprises reacting (2-aminoethoxy)acetic acid with hydrogen cyanide and formaldehyde under acidic conditions followed by hydrolysis.
Yet in another aspect, the invention concerns a multi step process for the preparation of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX) which process comprises the steps of
(1) reacting 3-morpholinone with a base to form (2-aminoethoxy)acetic acid (Ib);
(2) alkylating (2-aminoethoxy)acetic acid salt formed in step (1) with formaldehyde to form [2-(hydroxymethylamino)ethoxy]acetic acid (II);
(3) reacting [2-(hydroxymethylamino)ethoxy]acetic acid salt formed in step (2) with hydrogen cyanide to form [2-(cyanomethylamino)ethoxy]acetic acid (III);
(4) hydrolysing [2-(cyanomethylamino)ethoxy]acetic acid formed in step (3) with a base to form N-[2-(carboxymethoxy)ethyl]glycine salt (V);
(5) reacting N-[2-(carboxymethoxy)ethyl]glycine formed in step (4) with formaldehyde and hydrogen cyanide to form N-[2-(carboxymethoxy)ethyl]-N-(cyanomethyl)glycine (VII); and
(6) hydrolysing N-[2-(carboxymethoxy)ethyl]-N-(cyanomethyl)glycine formed in step (5) with a base to form N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX).
This process is illustrated in Scheme I below.
Yet in another aspect, the present invention relates to aqueous hard surface cleaning compositions comprising N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX).
Still in another aspect, the present invention concerns a method of cleaning a hard surface by contacting said hard surface with an aqueous hard surface cleaning composition comprising N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX).
The compounds of the present invention represented by the formula 
wherein R and R1 independently represent H, xe2x80x94CH2CN or xe2x80x94CH2CO2X, with the proviso that R and R1 can not be both H or xe2x80x94CH2CO2X; and X represents hydrogen, an alkali metal or alkaline earth metal are useful as intermediates in the synthesis of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX).
One preferred embodiment of the compounds of the present invention is represented by the formula 
wherein X represents hydrogen, an alkali metal or alkaline earth metal.
Still another preferred embodiment of the compounds of the present invention is represented by the formula 
wherein X represents hydrogen, an alkali metal or alkaline earth metal.
Yet another preferred embodiment of the compounds of the present invention is represented by the formula 
wherein X represents hydrogen, an alkali metal or alkaline earth metal.
Starting materials for making the intermediate compounds of the present invention of formula IX include 3-morpholinone and hydrogen cyanide and formaldehyde, or glycolonitrile. A suitable reaction scheme for the synthesis of the intermediate compounds of the present invention is shown in Scheme I below. 
M in Scheme I independently in each occurrence represents an alkali or alkaline-earth metal.
In the multi step process of the present invention 3-morpholinone (Ia) is first contacted with a suitable base such as sodium hydroxide, followed by alkylation with formaldehyde and hydrogen cyanide to form [2-(cyanomethylamino)ethoxy]acetic acid (III). The molar ratio of 3-morpholinone (Ia) to formaldehyde and hydrogen cyanide is generally about 1:1.
The hydrolysis of [2-(cyanomethylamino)ethoxy]acetic acid (III) with a base gives N-[2-(carboxymethoxy)ethyl]glycine (V).
N-[2-(carboxymethoxy)ethyl]glycine (V) is then reacted with additional formaldehyde and hydrogen cyanide to form N-[2-(carboxymethoxy)ethyl]-N-(cyanomethyl)glycine (VII). The molar ratio of N-[2-(carboxymethoxy)ethyl]glycine (V) to formaldehyde and hydrogen cyanide is generally about 1:1.
In the above reactions, glycolonitrile can be substituted for formaldehyde and hydrogen cyanide.
N-[2-(carboxymethoxy)ethyl]-N-(cyanomethyl)glycine (VII) is then hydrolyzed using a base such as sodium hydroxide to give the alkali metal salt of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX). Hydrolysis of the cyanomethyl group proceeds through the amide intermediate as depicted by structure (VIII) in Scheme I, resulting in the formation of the carboxymethyl group, which liberates the easily removable ammonia.
The above reactions may be carried out in the presence of any base capable of hydrolyzing the nitrile functionality. Examples of suitable bases include alkali and alkaline earth metal hydroxides. Preferably sodium and potassium hydroxide are used in the above reaction scheme.
In addition to bases, the nitrile functionality can be hydrolyzed using strong acids such as hydrochloric acid or sulfuric acid. In this case, the ammonium salt of the respective acid is obtained as a by-product.
While reaction Scheme I shows the addition of one mole equivalent of base per mole of nitrile functionality, excess molar amounts of base can be used.
Preferably the alkylation reaction steps are carried out at a temperature from about 0 to 100xc2x0 C., preferably from about 15 to 65xc2x0 C. The hydrolysis of N-[2-(carboxymethoxy)ethyl]aminoacetonitrile (III) and N-[2-(carboxymethoxy)ethyl]-N-(cyanomethyl)glycine (VII) is generally done at a temperature from about 0 to about 120xc2x0 C. Preferably the hydrolysis step is done at a temperature from about 20xc2x0 C. to about 105xc2x0 C.
The hydrolysis of N-[2-(carboxymethoxy)ethyl]-N-(cyanomethyl)glycine (VII) to N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX) results in a conversion in excess of 90 percent. Although Scheme I indicates that the production of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine (IX) is done in step reactions, the production can be accomplished by adding glycolonitrile to an alkaline solution of 3-morpholinone (Ia) at a temperature to achieve alkaline hydrolysis. In this procedure, intermediate N-[2-(carboxy-methoxy)ethyl]-N-(cyanomethyl)glycine (VII) is rapidly converted to N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)-glycine (IX).
N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine is a chelant which will biodegrade in the semi-continuous activated sludge test (ASTM D-2667). In this test, a standardized sludge containing municipal waste treatment plant organisms is used to biodegrade the chelant in the presence of metal ions representative of those found in the environment. Such a test simulates the environment encountered in a municipal waste treatment plant for screening the inherent biodegradability of non-volatile water-soluble compounds.
The modified Sturm test, in a similar manner contacts the chelant with a standardized culture of microorganisms. The evolution of carbon dioxide is used as a basis for determining microbial degradation when the test chelant is used as the sole carbon source.
N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine as a chelant is useful, for instance, in food products vulnerable to metal-catalyzed spoilage or discoloration; in cleaning and laundering products for removing metal ions, e.g. from hard water that may reduce the effectiveness, appearance, stability, rinsibility, bleaching effectiveness, germicidal effectiveness or other property of the cleaning agents; in personal care products like creams, lotions, deodorants and ointments to avoid metal-catalyzed oxidation and rancidity, turbidity, reduced shelf-like and the like; and in pulp and paper processing to enhance or maintain bleaching effectiveness. N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine can also be used in pipes, vessels, heat exchanges, evaporators, filters and the like to avoid or remove scaling; in pharmaceuticals; in metal working; in textile preparation, desizing, scouring, bleaching, dyeing and the like; in agriculture as in chelated micronutrients or herbicides; in polymerization or stabilization of polymers; in photography, e.g. in developers or bleaches; and in the oil field such as for drilling, production, recovery, hydrogen sulfide abatement and the like. The amount of chelating agent employed in the above noted applications are known in the art.
The use of N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine is particularly advantageous in hard-surface cleaners applications for the control of alkaline-earth metals, particularly calcium, and in preventing scaling. Typical applications for N-[2-(carboxymethoxy)-ethyl]-N-(carboxymethyl)glycine include the use in cleaning compositions suitable for hard-surface cleaning, such as certain automatic dishwashing agents and kitchen or bathroom soil removal and calcium soap removal from bathtub surfaces. When used in hard-surface cleaning compositions, N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine generally constitutes at least about 0.1 weight percent of the cleaning composition and typically less than about 25 percent of the cleaning composition. Preferably the hard-surface cleaning composition comprises about 0.1 to about 15 percent N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine, and more preferably about 0.5 to about 5 percent.
In addition to being biodegradable, it has been found that N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine can be used in hard-surface cleaning compositions free of organic solvents. This is particularly advantageous in that cleaning can be done without the concern for release of organic solvent into the environment.
Hard-surface cleaning compositions containing N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine are usually at an alkaline pH with a range of about 8 to about 14. Preferably the pH of the cleaning composition is from about 9 to about 13, and more preferably from about 10 to about 12.
In addition to N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine, hard surface cleaning compositions of the present invention can optionally contain additional additives well known in the art. For example, surface-active agents, are beneficial in a hard-surface cleaner.
Such surface active agents include water-soluble surfactants such as synthetic anionic, nonionic, cationic, amphoteric and zwitterionic surfactants and mixtures thereof. Exemplary surfactants include the alkyl benzene sulfates and sulfonates, paraffin sulfonates, olefin sulfonates, alkoxylated (especially ethoxylated) alcohols and alkyl phenols, amine oxides, sulfonates of fatty acids and of fatty acid esters, and the like, which are known in the detergency art. Preferably, such surfactants contain an alkyl group in about the C10-C18 range. Anionic surfactants are commonly used in the form of their sodium, potassium or triethanol ammonium salts. The nonionics advantageously contain from about 3 to about 17 ethylene oxide groups per mole of hydrophobic moiety. Representative cationic surfactants include quaternary ammonium compounds such as ditallow dimethyl ammonium chloride, and are preferably used in combination with nonionic surfactants. Preferred in the composition are about C12-C16 alkyl benzene sulfonates, about C12-C18 paraffin-sulfonates and the ethoxylated alcohols of the formula RO(CH2xe2x80x94CH2O)n, with R being a C12-C15 alkyl chain and n being a number from 6 to 10, and the ethoxylated alcohol sulfates of formula ROxe2x80x94(CH2xe2x80x94CH2O)nxe2x80x94SO3M, with R being a C12-C18 alkyl chain, n is a number from about 2 to about 8, and M is H or an alkali metal ion.
Anionic surfactants are advantageously present at levels from about 0.3 percent to about 8 percent of the hard surface cleaning composition. Nonionic surfactants, are preferably used at levels between about 0.1 percent to about 6 percent by weight of the composition. Mixtures of surfactants are also useful.
Other optional ingredients include detergent builders within the skill in the art including nitrilotriacetate (NTA), polycarboxylates, citrates, water-soluble phosphates such as tri-polyphosphate and sodium ortho- and pyro-phosphates, silicates, ethylenediaminetetraacetate (EDTA), aminopolyphosphonates, and mixtures thereof.
Other optional additives for the hard surface cleaning compositions include detergent hydrotropes. Exemplary hydrotropes include urea, monoethanolamine, diethanolamine, triethanolamine and the sodium, potassium, ammonium and alkanol ammonium salts of xylene sulfonates, toluene sulfonates, ethylbenzene sulfonates and isopropylbenzene sulfonates.
The hard-surface cleaning compositions of the invention also optionally contain an abrasive material. The abrasive materials include water-insoluble, non-gritty materials known for their relatively mild abrasive properties. It is preferred that the abrasives used herein not be undesirably xe2x80x9cscratchyxe2x80x9d. Abrasive materials having a Mohs hardness of no more than about 7 are preferred; while abrasives having a Mohs hardness of no more than about 3, are useful to avoid scratches on finishes such as aluminum or stainless steel. Suitable abrasives include inorganic materials, especially such materials as calcium carbonate and diatomaceous earth, as well as materials such as Fuller""s earth, magnesium carbonate, China clay, actapulgite, calcium hydroxyapatite, calcium orthophosphate, dolomite and the like. The aforesaid inorganic materials can be described as xe2x80x9cstrong abrasivesxe2x80x9d. Organic abrasives such as urea-formaldehyde, methyl methacrylate melamine-formaldehyde resins, polyethylene spheres and polyvinylchloride are advantageously used to avoid scratching on certain more delicate surfaces, such as plastic surfaces. Preferred abrasives have a particle size range of about 10-1000 microns and are preferably used at concentrations of about 5 percent to about 30 weight percent of the hard surface cleaning compositions.
Thickeners are preferably used to suspend the abrasives. Levels of thickener difficult to rinse from the cleaned surfaces are undesirable. Accordingly, the level is preferably less than about 2 percent, preferably from about 0.25 to about 1.5 percent. Exemplary thickeners include polyacrylates, xanthan gums, carboxymethyl celluloses, swellable smectite clay, and the like.
Soaps, especially soaps prepared from coconut oil fatty acids are also optionally included in the hard surface cleaners.
Optional components include components within the skill in the art to provide aesthetic or additional product performance benefits. Such components include perfumes, dyes, optical brighteners, soil suspending agents, detersive enzymes, gel-control agents, thickeners, freeze-thaw stabilizers, bactericides, preservatives, and the like.
The hard-surface cleaning compositions of the invention are advantageously in the form of liquid compositions, preferably aqueous compositions, including concentrates, containing as the essential ingredient N-[2-(carboxymethoxy)-ethyl]-N-(carboxymethyl)glycine. Preferably a surfactant is also present, more preferably in a concentration that corresponds to from about 2 to about 6 percent surfactant. Concentrated liquid compositions preferably contain from about 6 to about 10 percent surfactant.
Alternatively, the compositions herein are in the form of creamy scouring cleansers, preferably containing an abrasive material, surface-active agent, and N-[2-(carboxymethoxy)ethyl]-N-(carboxymethyl)glycine.
The cleaning compositions can be packaged in a container that comprises a means for creating a spray, e.g., a pump, aerosol propellant or spray valve. The composition can be thus conveniently applied to the surface to be cleaned by conventional means, such as wiping with a paper towel or cloth, without the need for rinsing.